Time machine backup external hard drive error

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Level 1

8 points

Time machine backup external hard drive error

Hello,
While in a hurry to catch a flight I accidentally unplugged my external hard drive (which I use for time machine backups) before ejecting. Now home, the time machine backup doesn't recognize my external drive. I went into disk utility to try to repair the disk. Here is what it says:

Verifying and repairing partition map for “Time Machine External Hard Drive”Checking prerequisitesChecking the partition listAdjusting partition map to fit whole disk as requiredChecking for an EFI system partitionChecking the EFI system partition’s sizeChecking the EFI system partition’s file systemChecking the EFI system partition’s folder contentChecking all HFS data partition loader spacesChecking booter partitionsReviewing boot support loadersChecking Core Storage Physical Volume partitionsUpdating Windows boot.ini files as requiredThe partition map appears to be OK

Verify and Repair volume “Time Machine”Repairing file system.File system check exit code is 8.Updating boot support partitions for the volume as required.Error: Disk Utility can’t repair this disk. Back up as many of your files as possible, reformat the disk, and restore your backed-up files.

I could really use some help as to how I should proceed. Any Advice?

Mac Pro, iOS 9.3.1

Posted on Sep 19, 2016 7:21 PM

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Answer 1

Sep 19, 2016 7:43 PM in response to Jes_R

I think you need to erase that Backup drive, and while you are doing that and making a full backup (which takes all afternoon to all night) you will be working without a net. If you do it in idle time, and after you have checked your Boot Drive, the risk of a catastrophic failure while making that Backup is low. Start now and by tomorrow you will have a Backup.

If you have another backup drive, add it and Time Machine will create a new independent backup on it, and then Time Machine will alternate drives automatically.

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Answer 2

Jes_R Author

Level 1

8 points

Sep 20, 2016 9:10 AM in response to Grant Bennet-Alder

Thank you for taking the time to respond. I actually tried to erase the disk and the disk utility failed to erase the disk. The message was: disk could not be unmounted.

Also- when erasing a disk, what format should you choose?

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Answer 3

Sep 20, 2016 9:25 AM in response to Jes_R

The 'disk cannot be unmounted' because it has open files and is in use. Try a Restart first. If no joy, you may have to use the version of Disk Utility in Recovery Mode to be certain the disk will not be busy.

Time Machine requires GUID partition Map and Mac OS Extended (journaled) format. Luckily, those are also the defaults.

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Answer 4

Jes_R Author

Level 1

8 points

Sep 20, 2016 9:29 AM in response to Grant Bennet-Alder

Hi!
I actually have restarted the computer 3 times but I can try one more time. Will keep you posted. Thanks for the update on the format, that is what I thought but I wanted to make sure since I don't really know.

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Answer 5

Jes_R Author

Level 1

8 points

Sep 20, 2016 9:35 AM in response to Grant Bennet-Alder

I did the restart again and the disk utility could still not unmount the disk

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Answer 6

Sep 20, 2016 10:28 AM in response to Jes_R

Then Restart and hold down Command-R at Restart. This will invoke Recovery mode, which runs a minimal set of Utilities from a separate partition on your Boot drive.

Full-blown Mac OS is not available, so your external drive will not be busy. Invoke Disk Utility from there, and your external drive can be Erased and/or Partitioned.

when completed, you can restart into Mac OS again, and start a Backup.

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Answer 7

Jes_R Author

Level 1

8 points

Sep 20, 2016 7:05 PM in response to Grant Bennet-Alder

This worked great! Thanks so much. Really appreciate the help!

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